The pressure switch is a small but critical safety component in a gas furnace that ensures proper venting and inducer motor operation before ignition. This article explains step-by-step testing procedures, symptoms of a failing pressure switch, required tools, safety precautions, and troubleshooting tips to help diagnose issues accurately. Testing furnace pressure switch procedures are presented for technicians and informed homeowners seeking reliable, safe diagnostics.
| Symptom | Likely Cause | Quick Test |
|---|---|---|
| Furnace Fails To Ignite | Open Pressure Switch | Measure continuity with multimeter |
| Short Cycling Or Lockout | Intermittent Switch Closure | Watch voltage during inducer run |
| Inducer Runs But No Ignition | Blocked Vent/Tube Leak | Inspect hose and vent draft |
Schedule annual furnace inspections to clean inducer components, check vent terminations, and replace brittle tubing. Keeping filters clean and ensuring proper combustion air supply reduces inducer strain and lowers the likelihood of pressure-related faults.
When To Call A Professional
If troubleshooting points to gas valve, control board, or combustion issues beyond basic pressure switch diagnostics, a certified HVAC technician should be engaged. Professionals can safely perform gas manifold checks, combustion analyzers, and complex electrical diagnostics.
Key Takeaways For Effective Testing
Testing furnace pressure switch requires a methodical approach: visual inspection, verification of inducer operation, electrical continuity checks, and pressure measurement. Address tubing and venting issues first, bench-test suspect switches, and match replacement parts carefully. Prioritize safety and professional assistance for gas-related or complex failures.
Useful References And Further Reading
- ASHRAE Standards — Guidelines on HVAC safety and combustion air.
- NFPA Codes — National Fire Protection Association publications for combustion and venting.
- ACCA Manuals — Professional HVAC diagnostic and service practices.